Brake mechanism



2 Sheets-Sheet l I NV EN TOR FRANK L. MAIN ATTORNE F. l.. MA'INBRAKE'MECHANISM Filed sept. 29, 1957\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\Ill I Jan. 9, 1940.

F. L.. MAIN BRAKE MECHANISM Filed Sept. 29, 1937 2 Sheets-Sheet 2 n A/(/\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\Y l Patented Jan.9, ,1940 l f UNITED; STATES@ PfMaurv gOFFICE f BRAKE MEonA'NIsM, Q vFrank L, Birmingham,*'Mlchgfassignor to l KelseyeHayes Wheel Company,"DetrotyMch'.; a corporation' Delawapgl Y f .K y i= Applicationseptember 29, Y1937, semina. mensa ,v solapas. `(.01.,1ra-fraye Thisinvention relates generally to brake mech- The foregoing,vasf,well"a'sfother objects,v Will be anism and refers' moreparticularly to improvee; made more apparent as this descriptionproments inthe actuator for the brake -friction .ceeds, especially whenconsidered in connection j means. with theraccornpanying'drawings,wherein: l y One ofthe principal objects-of the present in-H 1 Figure 1is a side elevational view, partly in 5 rvention-resides in theprovision. of brakeiactuat` section, of a brake drum equipped with brakeing mechanism of the linkv and lever type so conmechanism constructed inaccordance with this structed and arranged that va more advantageousinveriizipxi;v n j l n* i actuatinglangle for thebrake friction means isf Figure 21s a Isectional View taken substantially provided.Inaccordance with this invention, the `V:on ,the plane indicated bytheline 2-2 of Fig- 10 n' actuator is effective in the forward directionofl K ure 1; .f e f l,

rotation to apply a force to ythe adjacent end of Figure 3 is asectionalview taken substantially the leading portion of the-brake frictionmeans; on the plane indicated by the' line r`33 "of Figvi'n a directionpredetermined to insure smooth'.A ure1.;. controllable action of thisportionl of the friction FigureflH isa sectional ,View ,takenSubstantially 15 means and, in the reverse direction of rotation of.v4onthe plane indicated by the rline 4-4' of Figthe'drum,to Vapply aforceto theadjacent end ure 1;, y y of the trailing' shoerv ata slightpositive iangle in Figure is a `sectional view :taken substantiallyorder to insure stoppingof the Vehicle inreverse f Von theplaneindicated by the line 5-f5 of Figure with arelativeiy nght pedalpressure. 1;andf v u, 2o

' vAnothery advantageous feature rof Athis inven-` l Figure 6 isafragmentary side elevational view tion resides in-the provision ofbrakefmechanism of a slightly modified form of construction. embodyingbrake shoes Aand-having anadjust-y The brake selected Vherein for thepurpose of ment device" and VLan actuator of thetype previ-.illustrating the presenti invention is provided with ously set forth,frespectively, associated with op. a brake drum Illv having fan annularIaxially ex- 25 Vpositeen'ds of the shoes inA such a'manner as totending brakefflange I I and having a web I2 render it `possible toutilize v:symmetrical shoes formed withfan opening I3 through thecentral and linings, as well asia lining-attack angle for f portionthereof for receiving a Wheel spindle I4.

"the actuator endsfofthe shoes, which .is sufv.Infaccordance withconventional practice, the cient'to provide'asmooth controllablebrake.yrear sidev of thefdrum is `closed by a backing 30 A further object ofthe present invention replate I5 having an opening ltherethrough in fsides in theprovision of actuating mechanism of alignment withV theopening I3 inthe web of the i thelink and lever typeinterconnecting theactu- VVbrake drumto permit the spindle I4 to extend ator ends of thebrake'friction means and proporl through the drum and having abolting-on pory tioned't'o provide a'receding leverage'as the brakeltion surrounding the'opening I6 adapted to be 35 friction meansapproaches the brake flange of 1 ysecured to thev spindle Il.`AIn'Figure 4 of the v*the drum.. Onel of .the outstandingA advantages.drawings, the spmdle is shown as connected to `derived by yemployingreceding leverage means is the axle of `thevehicle by means oi a.king'pin I'I y w f thatfitpermits' the vactuating cable to leave thearranged on an upA and down axis predetermined `40 1 backing plate: ofthe brake drum at the top of the to provide for the proper turning ofthe wheel and 40 pkingpin' and, in'addition, permits the primaryassociated brake drum.v i

4shoe'tofengagethe.drum at the lower side-of the lIuhe A.backing plateI5 forms a support for the 'latter,.which is=the most desirable portionof thel brake. mechanism and' thev latter is shown in drum .from thelstandpoint" of veffective braking!A Figure 1 as including a pair ofbrake shoes I9 and f In, addition,`v the receding leverage actuator con-2II. In the present instance, the shoes are sub- 45 .serves pedalrtravelwhen the drum expands due st'antially T-shape'd in cross section and aresup- 1 to heatl by reducing the actuating leverage.y ported .on thebacking plate within the drum with .Afurther objectof this .inventionresides inthe thekaxially extending portions `2I located adjaprovisionof a brake yoffering the possibility off cent thein'nersurfa'ceof thebrake flange II on .employdng an. actuator having. a substantially. thedr1nn jA`]brake' lining 22 having the desired 50 i. uniform leveragethroughouty Vbrake u operation. co-eflicient 'of friction is secured tothe outer sur- This ltype of leverage is particularly advantage-y .faceof each ofthe axially extending portions 2| vous Whenthe brake isdesigned forruse on ve. of the shoes for engagement with the innerannuhicles where a relatively` light pedal pressure isr lar. surface ofthe brake flange II when the shoes desired for vdeceleration from allspeeds." 'y l aremoved radially outwardly relative to the drum. 55

o row 26.

Referring again to Figure 1 of the drawings, it' will be noted that theopposite ends of the shoes arespaced from each other circumferentiallyof the drum and that the two shoes, as well as the linings carriedthereby, are symmetrical with respect to the axis of rotation of thedrum. In other words, the two shoes are interchangeable and this isdesirable from the standpoint of manufacture, since it reduces thenumber of differently designed parts to the minimum.

An adjustment anchor device 23 is supported on the backing plate I5between the ends of the \brake shoes at one side of the drum, and anactuator 24 is associated with the ends of the brake shoes at theopposite side of the drum. Both the adjustment anchor device andactuator permit circumferential shifting movement of the brake shoes inthe forward direction of rotation of the brake drum, designated inFigure 1 by the ar- The construction is such that when the brake shoesare moved by the actuator into engagement with theI brake fiange II ofthe drum in the forward direction of rotation of the latter, torque istransferred from the primary shoe I9 through the adjustment device 23 tothe secondary shoe 20, and the resulting servo action assists inapplying the brake friction means. On the other hand, when the brakefriction means is applied in the reverse direction of rotation of thebrake drum by the actuator, the adjustment device 23 anchors the shoeson the backing plate I5 and a symmetrical brake results.

The adjustment anchor device 23, aside from anchoring the brake shoes inthe reverse direction of rotation, also functions to move the shoesoutwardly relative to the brake drum to vary the clearance between thebrake linings and the innerannular surface of the brake flange I I. Theshoes are moved by the adjustment device about an abutment 21 secured tothe backing plate between the actuator ends of the shoes and en--gageable with the latter ends of the shoes. The abutment 21 is in theform of a stud which is secured to the backing plate for limited radialdisplacement relative thereto in order to insure proper centering of thebrake friction means within the brake drum.

In the present instance, the adjustment device 23 comprises a bracket 28having an axially bored portion 29 extending out of the drum through anopening 30 in the backing plate and having tubular extensions 3Iextending at right angles to the axis of the bore in substantialalignment with the adjustment ends of the brake shoes. The extremitiesof the web portions of the adjustment ends of the shoes project into theouter ends of the extensions and are recessed, as at 32, to provide abearing engagement with the adjacent ends of the links or plungers 33.The plungers 33 are slidably supported in the extensions 3i, and theadjacent ends of the plungers are engaged by a Wedge 34 movable axiallyof the bore in the bracket by means of a screw 35 threaded in theportion 29 of the bracket and accessible for manipulation from a pointexteriorly of the backing plate.

It may be pointed out at this time that the adjustment anchor devicemaintains the adjustment ends of the shoes in such spaced relation toeach other that an attack angle" A for both shoes is provided which issufficient. to secure smooth brake operation. The attack angle of abrake shoe depends upon the location of the fulcrum about which the toeof the shoe swings into engagement with the drum and also depends uponthe' location of the toe end of the brake friction means on the shoe.Briefly, the attack angle" is the instantaneous angle at which the toeend of the friction means on the shoe contacts with the drum as the shoeis swung into engagement with the drum. In other words, the attack angleis the angle that exists between a line drawn from the fulcrum point ofthe shoe to the toe of the friction means and a line tangent to thisline at the point of contact of the toe. with the brake drum. In theinterests of clarity, the angle is usually indicated as the anglebetween a line connecting the toe of the brake friction means with thefulcrum point of the shoe and a radius of the drum passing through thetoe ofthe brake friction means. For the purpose of illustration, I haveshown the attack angle" for each shoe as being approximately 23 and thisis accomplished in a construction where the shoes and linings are sym-`letrical or interchangeable,

It has previously been stated that the adjustment anchor device rendersit possible to trans mit torque from the primary shoe to the secondaryshoe in the forward direction of rotation and serves as an anchor forthe shoes in the reverse direction of rotation. Upon reference to Figure3, it will be noted that the opening 30 through the backing plate issufficiently larger than the diameter of the portion of the bracketextending therethrough to permit the shifting movement of the bracketrequired in the forward direction of rotation to transfer the torque. Inthe reverse direction of rotation, the bracket anchors against the side36 of the opening 30. In this connection, attention may be called to thefact that the adjustment ends of the shoes are normally yieldablymaintained into engagement with the plungers 33 by means of theretracting springs 38 and 39. The outer ends of these springs arerespectively connected to the adjustment ends of the shoes, and theinner ends of the springs are connected to a stud 49 secured to thebacking plate. The stud 40 is offset in a direction toward the primaryshoe I9 from a plane including the axis of rotation of the drum and theaxis of the wedge so that the spring 38 will exert a greater force onthe secondary shoe. In other words, the spring 38 maintains the bracket28 in contact with the side 36 of the opening 3U.

In the present instance, the actuator 24 is of the link and lever type.This actuator comprises a lever 4I having one end pivotally connected tothe shoe 20 adjacent the actuator end of the latter by means of a pivot42 .and having the opposite end connected to a suitable control (notshown) by means of a cable 43. I'he cable 43 extends out of the drumthrough the backing plate at a point substantially in alignment with theaxis of the kingpin I'I and the arrangement is such that movement of thecable in the direction of the arrow 44 reduces the effective leveragearm, designated in Figure l by the reference character B. The lever 4Iis operatively connected to the primary shoe by means of a link 45having one end engaging in a recess 4G in the lever 4I adjacent thepivot 42 to provide a fulcrum for 'the lever 4I spaced from the pivot 42the length of the short lever arm. identified in Figure l by thereference character C. The 0D- posite end of the link is fulcrumed. asat 4l. on

the'actuator end of the primary shoe I9 at awint:

line passing through the axis of the abutment and the axisvof rotationof the drum. At this time it vmz'i'y-'be pointed out that the actuatingangle of a shoe can be dened as the angle between a line perpendicularto the radius of the brake drum passing through the axis of the abutmentuponr which the shoe seats when released and a line representingthedirection in which the actuating force is applied to the shoe. The

actuating angle is termed a positive angle if it is radially :outwardlyof the perpendicular. In

Figurell, the actuating angle for the' primaryl shoeV is substantiallyzero with the result that the shoe has a smooth action against thebrake'flange and'will not grab, as would be the case if the force ywereapplied at a positive angle, as in the direction of the dotted line E.

Assuming now that the brake drum is rotating in the reversedirection'and that the lever 4I is end of the shoe 2D at a positiveactuating angle G when the drum is rotating in the reverse directionand, while this will effect a slight grabbing action, nevertheless, thisis desirable instead of being objectionable in the reverse direction ofrotation, especially in cases where no torque is transferred in reverse,because it renders'braking more e'ective with a relatively light pedalpressure.

Reference has also been made above to the fact that the lever 4I is ofthe receding type in that the internal leverage is reduced as the brakeshoe approaches engagement with the brake iiange Il. In this connection,it will be noted from Figure 1 that at the start of movement of thelever 4| in a direction to expand the shoes into engagement with thedrum, the leverage ratio is whereas at the completion ofthe movement ofthe leverI v4 l.indicated by the dotted lines in Figure 1, the leveragearm B has been reduced in length, aslindicated by the letter H, and theleverage arm C has been'increased in length to the extent indicated bythe leverage arm I. In other words, the internal leverage vhas beengradually reduced from the leverage ratio tained into engagement withthe abutment 21 by means of n pair of retraction springs 50 and 5l.

'Ihe outer ends of these springs are, respectively, connected to theshoes I9 and 20 and the inner ends of the springs are connected to anabutment 52 secured to the backing plate at a point offset toward theprimary shoe from the plane including the axisv of the stud 21 and axisof rotation of the drum. The arrangement is4 such that the spring 50exerts a greater force on the secondary kshoe 20 than the spring 5Iexerts on the primary shoe and, as a result, the primary shoe is movedoutwardly ahead of the secondary shoe. Y Y

The embodiment of the invention illustrated in Figure 6 shows a brakeconstruction similar to the one previously described, with the exceptionthat the lever 4I is of the constant leverage type and the includedangle between the lever and the cable is maintained substantially-constant throughout the brake application. This 4modification may beadvantageously used in cases v 'Where it is desired to decelerate thevehicle at all speeds with a relatively light pedal pressure and, as aconsequence, renders control of the brakes easier during emergency highspeed stops.

What I claim as my, invention is:

yl. In brake mechanism', a brake drurn rotatable in opposite directions,brake friction means supported within said drum for movement relative tothe latter into engagement therewith and having spaced ends, and anactuator of the link and lever type interconnecting said ends andeffective =n the forward direction of rotation of the drum to move theend of the leading portion of the friction means into engagement withthe drum at a substantially zero actuating angle and upon reversedirection of rotation of the drum to move the adjacent end of thefriction means into engagement with the drum at a positive actuatingangle. Y

2. In brake mechanism, a revoluble brake drum, a pair of brake shoeslocated within the drum and movable relative to the drum into engagementtherewith, means supporting the brake shoes in the drum with the primaryshoe at the ground side of the drum and with the adjacent ends of theshoes in spaced relation to each other, adjustment means located betweenthe ends of the shoes at one side of the drum providing for outwardmovement of the shoes into engagement `with the drum, and an actuator ofthe link and lever type interconnecting the opposite ends of the shoesand effective to move the primary shoe outwardly relative to the brakedrum into engagement therewith at a substantially zero actuating angle.

3. In brake mechanism, a revoluble brake drum, a pair of brake shoeslocated within the drum and movable relative to the drum intoengagement'therewith, means supporting the brake shoes in the drum withthe primary shoe at the ground side of the drum and with the adjacentends of the shoes inspaced relation to eac-h other.

adjustment means located between the ends of the shoes at one side ofthe drum providing for outward-movement of the shoes into engagementwith the drum, and an actuator of the link and leverItype'interconr'iectingl the opposite ends of the shoes and eflective'tomove the primary shoe outwardly into engagement with the drum at asubstantially zero-'actuating angle and to move the secondary shoeintoengagement with the drum at a positive actuating angle.

4. In brake mechanism, a brake drum rotatable in opposite directions,brake friction means located within the drum and movable relative tofriction means in the reverse direction of rota tion, andan actuator ofthe link and lever type interconnecting said ends of the friction meansand effective to move the end of the leading portion of the frictionmeans into engagement with the drum at a substantially zero actuatingangle and effective in the reverse direction of rotation of the drum tomove the opposite end of the friction means into engagement withthe'drum at a substantially positive actuating angle.

5. In brake mechanism, a brake drum rotatable in opposite directions,brake friction means supported within 'said drum for movement relativeto the latter into engagement therewith and having spaced ends, anactuator of the link and lever type interconnecting said ends andcomprising, a lever pivotally connected to the end of the trailingportion of the'friction means, and a link having one end providing afulcrum for said lever and having the` other end operatively con nectedto the leading end of the friction means,

said lever and link being arranged to actuatewithin the drum forshifting movement circumferentially of the'drum in the direction offorward rotation of the latter and having spaced ends, a backing platefor the drum, an adjustment anchor device extending through an enlargedopening in the backing plate kbetween adjacent ends of the shoes andshiftable with the shoes in I Y the adjacent end of thesecondary shoeinto enthe forward direction of rotation of the drum, and an actuator ofthe link and lever type interconnecting the opposite ends of the shoesand eiective in the forward direction of rotation to move the end of theleading shoe toward the drum at a substantially zero actuating angle andeffective in the. reverse direction of rotation of the drum warddirection of rotation of the drum and toy serve as an anchor for takingthe torque of the secondary shoe upon reverse rotation of the drum,

` and an actuator of the link and lever type interconnecting theopposite ends of the shoes and effective in the forward direction ofrotation of the drum to move the leading end of the primary shoe intoengagement with the drum at a substantially zero actuating angle and-upon reverse rotation of the drum to move' the adjacent end of thesecondary shoe into engagement with the drum at a positive actuatingangle.

8. In brake mechanism, a revoluble brake drum, a backing plate, a pairof brake shoes supported within the drum for movement relative to thelatter into engagement therewith and having the opposite ends spacedfrom each other, a bracket supported upon the backing plate between theends of the shoes at one side of the drum and having a limitedcircumferential movement relative to the backing plate, a spring urgingthe bracket toward the primary shoe to permit a limited servo actionupon forward rotation of the brake drum, and an actuator of the link andlever typeinterconnecting the opposite ends of the shoes and effectivein the forward direction of rotation of the drum to move the leading iend of the primary shoe into engagement with vthe drum at asubstantially zero actuating angle and upon reverse rotation of the drumto move gagement with the drum at a positive actuating angle.

FRANK L. MAIN.

